Embodiments of the present invention generally provide an inductively coupled plasma (ICP) reactor having a substrate RF bias that is capable of control of the RF phase difference between the ICP source (a first RF source) and the substrate bias (a second RF source) for plasma processing reactors used in the semiconductor industry. Control of the RF phase difference provides a powerful knob for fine process tuning. For example, control of the RF phase difference may be used to control one or more of average etch rate, etch rate uniformity, etch rate skew, critical dimension (CD) uniformity, and CD skew, CD range, self DC bias control, and chamber matching.